Bromodomain-containing proteins are of substantial biological interest, as components of transcription factor complexes and determinants of epigenetic memory. For example, the bromo and extra terminal (BET) protein family (e.g., bromodomain-containing protein 2 (BRD2), bromodomain-containing protein 3 (BRD3), bromodomain-containing protein 4 (BRD4), and bromodomain testis-specific protein (BRDT)) shares a common domain architecture featuring two amino-terminal bromodomains that exhibit high levels of sequence conservation, and a more divergent carboxy-terminal recruitment domain (Filippakopoulos et al., Nature 2010, 468, 1067-1073). BRD2 and BRD3 are reported to associate with histones along actively transcribed genes and may be involved in facilitating transcriptional elongation (Leroy et al., Mol. Cell. 2008, 30, 51-60). It has also been reported that BRD4 or BRD3 may fuse with nuclear protein in testis (NUT), forming novel fusion oncogenes BRD4-NUT or BRD3-NUT, in a highly malignant form of epithelial neoplasia (French et al., Cancer Res., 2003, 63, 304-307; French et al., J. Clin. Oncol. 2004, 22, 4135-4139). Data suggests that BRD-NUT fusion proteins contribute to carcinogenesis (French et al., Oncogene 2008, 27, 2237-2242). BRDT is uniquely expressed in the testes and ovary. All family members of BET have been reported to have some function in controlling or executing aspects of the cell cycle and have been shown to remain in complex with chromosomes during cell division, suggesting a role in the maintenance of epigenetic memory. In addition, some viruses make use of BET proteins to tether their genomes to the host cell chromatin, as part of the process of viral replication (You et al., Cell 2004, 117, 349-360). BRD4 appears to be involved in the recruitment of the pTEF-b complex to inducible genes, resulting in phosphorylation of RNA polymerase and increased transcriptional output (Hargreaves et al., Cell 2009, 138, 129-145). In humans, BRD2, BRD3, BRD4, and BRDT exhibit similar gene arrangements, domain organizations, and some functional properties (Wu et al., J. Biol. Chem. 2007, 282, 13141-13145).